1. Field of the Invention
The present invention relates to novel foam products and, more particularly, to highly absorbent hydrophilic polyurethane foam compositions which have liquid release and exchange characteristics.
2. Background of the Invention
Absorbent pads, such as for use in contact with the skin for absorbing body fluids, are well known. Such pads are useful for numerous applications, including for example as a diaper, sanitary napkin, bandage, wound dressing or the like.
Absorbent pads have been made of a wide variety of materials. For example, such pads have been made using graft copolymers, as described in U.S. Pat. No. 4,055,184. The absorbent pad therein described includes an absorbent mass comprising a solid finely-divided mixture of a completely hydrolyzed starch-polyacrylonitrile graft copolymer and a non-irritating and non-toxic water-soluble basic material such as, for example, sodium bicarbonate which may be admixed with and distributed in a highly porous web or batt of cotton linters, layers of creped tissue or a mass of shredded polyurethane foam particles.
Pads in the form of a foam and which have been made from various superabsorbent materials are likewise known. For example, U.S. Pat. No. 4,394,930 discloses an absorbent foam product prepared by mixing together a solid, particulate, water-insoluble, water-swellable polymer such as "hydrogels", "hydrocolloids" or "superabsorbents" which are lightly cross-linked polymers containing a plurality of hydrophilic groups, such as carboxyl, carboxamide, sulfonate salt or hydroxyl groups, a blowing agent, and a liquid polyhydroxy organic compound and allowing the mixture to foam.
Polyurethane foams, treated and/or prepared in a manner so as to render them hydrophilic are also known. For example, U.S. Pat. No. 3,586,648 discloses a hydrophilic polyurethane foam prepared by the so-called "one-shot" technique and is stated to include a carboxymethyl cellulose or a carboxymethyl cellulose salt.
U.S. Pat. No. 4,497,914 discloses an ostomy gasket composition derived from the non-aqueous reaction of a polyisocyanate and a polyoxyalkylene polyol. A hydrophilic filler, such as hydroxyethylcellulose, hydroxypropylcellulose or mixtures thereof, are incorporated into the polyol phase prior to reaction.
Hydrophilic cross-linked polyurethane foams are disclosed in U.S. Pat. No. 3,903,232. Such foams are prepared by reacting particular isocyanate-capped polyoxyethylene polyols having an isocyanate functionality greater than two with large amounts of an aqueous reactant, preferably water. The foam is said to be useful for the absorption of body fluids and may be used for external body cleaning, for internal body usage, such as is necessary in dental and medical applications, and as intimate absorptive products such as diapers, sanitary napkins, catamenial devices and the like.
Other adsorbent pads using hydrophilic foam include U.S. Pat. No. 3,961,629, which discloses a hydrophilic polyurethane foam in which the foam pores have a surfactant coating to accelerate absorption of body fluids into the pores at medically acceptable rates. The foam is rendered hydrophilic by coating the pore walls with a thin layer of a surfactant. Hygroscopic agents such as glycerine as well as other agents, such as germicidal and therapeutic agents, may be incorporated into the foam.
U.S. Pat. No. 4,664,662 discloses an absorbent wound dressing which comprises an absorbent foam material retained in a water permeable, porous bag. The absorbent foam is preferably a hydrophilic polyurethane foam which can be made from HYPOL isocyanate-capped polyether prepolymer marketed by W. R. Grace and Co. and non-ionic surfactants. Physiologically active components such as local anaesthetics, antibacterial agents, antifungal agents and the like which are compatible with the absorbent material may be incorporated into the wound dressing.
Hydrophilic polyurethane foam compositions are also disclosed in U.S. Pat. No. 4,339,550. The hydrophilic foam composition is prepared by the "in situ" reaction of an isocyanate-capped polyether prepolymer having a functionality of from about 2 to about 8, water, and a chemically compatible, essentially non-polar, volatile organic compound. The foam is stated to be capable of achieving a sustained, controlled release of the volatile materials from the foam structure. Suitable "control release" ingredients for use in controlling the rate of release of the volatile ingredients include polyols, such as propylene glycol and glycerin, and materials classified as gums.
Despite the wide variety of known absorbent pads and polyurethane foam compositions there still remains a need for a highly absorbent hydrophilic polyurethane foam composition which releasably carries an adjuvant and which is capable of both absorbing an external liquid and releasing the adjuvant carried by the foam composition in the presence of the external liquid.
Accordingly, it is a principal object of the present invention to provide a polyurethane foam composition which is hydrophilic, highly absorbent and which releasably carries an adjuvant which is capable of being released from the foam in the presence of an external liquid which is preferentially absorbed by the foam composition. A more detailed object of the present invention is to provide a foam composition which is capable of releasing an adjuvant to a designated situs and which is capable of absorbing external liquids from that situs. A related object is to provide such a polyurethane foam composition which will tightly hold the external fluid once it is absorbed.
Another object of the invention is to provide a hydrophilic foam composition that can be prepared at ambient temperature.
It is a further object of the present invention to provide a wound dressing using a highly absorbent hydrophilic polyurethane foam composition. It is yet another object of the present invention to provide such a foam composition which includes a therapeutic, cosmetic or other like agent for release to and treatment of the situs of application. A still further object is to provide a foam composition which has hemostatic, bacteriostatic, emollifying, demulcifying and wound cleansing properties.
It is yet another object to provide a method of treating a wound by applying to the wound a wound dressing which includes a hydrophilic foam composition as described herein.
A further object of the present invention is to provide a composite for use in a wound dressing which includes a hydrophilic foam composition as described herein. Another object is to provide a method for making such a composite.
These and other objects and advantages of the present invention will be apparent from the following description of the invention.